Channel state feedback method and apparatus in communication system

ABSTRACT

A method and an apparatus for feeding back channel state information (CSI) of user equipment (UE) in a communication system are disclosed. The method comprises the steps of: receiving, from a base station, configuration information related to a plurality of CSI reports; identifying the setting of the plurality of CSI reports corresponding to a plurality of measurement resources, on the basis of the configuration information; generating a first CSI report corresponding to a first measurement resource and a second CSI report corresponding to a second measurement resource when the plurality of CSI reports are set; and transmitting the first CSI report and the second CSI report to the base station.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 371 of International Application No.PCT/KR2018/004267 filed on Apr. 12, 2018, which claims priority to GreatBritain Patent Application No. 1707176.2 filed on May 5, 2017, thedisclosures of which are herein incorporated by reference in theirentirety.

BACKGROUND 1. Field

The present disclosure relates to a method and apparatus for signalingand receiving channel state information (CSI) feedback in coordinatedmultipoint (CoMP) systems.

2. Description of the Related Art

Non-coherent joint transmission (NCJT), which is a type of coordinatedmultipoint (CoMP) transmission, has a problem regarding CSI feedback.Multiple CSI reports are generally needed to conduct efficient radioresource allocation at coordinating base stations (BSs) because ofmultiple interference hypotheses. In other words, there are severaldifferent interference hypotheses, which should be reported back to thecoordinating BSs to ensure efficient resource management.

For a joint transmission (JT) scheme, the data for one user equipment(UE) may be transmitted from multiple transmission/reception points(TRPs) in the same time-frequency resource, where the transmission canbe performed in a coherent joint transmission way or an NCJT way. NCJTrefers to a case where data of multiple layers is independentlytransmitted to a UE from different transmission points through MIMOtransmission.

SUMMARY

Embodiments of the present disclosure may address shortcomings in theprior art, whether mentioned herein or not.

In particular, embodiments of the disclosure may address the problemsassociated with the magnitude of data required to fully provide channelstate information to the coordinating BSs.

Embodiments of the disclosure provide a method and apparatus foridentifying a correlation between CSI reports and efficientlycompressing a CSI feedback signaling overhead by using the identifiedcorrelation.

According to the present disclosure there is provided an apparatus andmethod as set forth in the appended claims. Other features of thedisclosure will be apparent from the dependent claims and thedescription which follows.

A method of transmitting channel state information (CSI) by a userequipment (UE) in a communication system according to an embodiment ofthe disclosure includes receiving configuration information related to aplurality of CSI reports from a base station (BS), determining based onthe configuration information that the plurality of CSI reportscorresponding to a plurality of measurement resources are configured,generating a first CSI report corresponding to a first measurementresource and a second CSI report corresponding to a second measurementresource, when the plurality of CSI reports are configured, andtransmitting the first CSI report and the second CSI report to the BS.

A UE that transmits CSI in a communication system according to anembodiment of the disclosure includes a transceiver configured toreceive configuration information related to a plurality of CSI reportsfrom a BS and a processor configured to determine based on theconfiguration information that the plurality of CSI reportscorresponding to a plurality of measurement resources are configured,generate a first CSI report corresponding to a first measurementresource and a second CSI report corresponding to a second measurementresource, when the plurality of CSI reports are configured, and transmitthe first CSI report and the second CSI report to the BS.

A method of receiving CSI from a UE by a BS in a communication systemaccording to an embodiment of the disclosure includes transmittingconfiguration information related to a plurality of CSI reportscorresponding to a plurality of measurement resources to the UE,receiving a first CSI report corresponding to a first measurementresource and a second CSI report corresponding to a second measurementresource from the UE based on the configuration information, andprocessing the first CSI report and the second CSI report.

An apparatus of a BS that receives CSI from a UE in a communicationsystem according to an embodiment of the disclosure includes atransceiver configured to transmit configuration information related toa plurality of CSI reports to the UE and receive a first CSI reportcorresponding to a first measurement resource and a second CSI reportcorresponding to a second measurement resource from the UE based on theconfiguration information and a processor configured to process thefirst CSI report and the second CSI report.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the disclosure, and to show howembodiments of the same may be carried into effect, reference will nowbe made, by way of example, to the accompanying diagrammatic drawings inwhich:

FIGS. 1A and 1B show, respectively, network configurations operating incoherent joint transmission and non-coherent joint transmissionconfigurations.

FIG. 2 shows signal and interference hypotheses corresponding todifferent network coordination methods.

FIGS. 3A and 3B show a method according to an embodiment of the presentdisclosure.

FIGS. 4A and 4B show a method according to an embodiment of the presentdisclosure.

FIG. 5 is a block diagram of a user equipment (UE) according to anembodiment of the present disclosure.

FIG. 6 is a block diagram of a base station (BS) according to anembodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, various embodiments of the present disclosure will bedisclosed with reference to the accompanying drawings.

When embodiments of the disclosure are described, technical matters thatare well known in a technical field of the disclosure and are notdirectly related to the disclosure will not be described. By omittingany unnecessary description, the subject matter of the disclosure willbe more clearly described without being obscured.

For the same reasons, some elements will be exaggerated, omitted, orsimplified in the attached drawings. The size of each element does notentirely reflect the actual size of the element. In each drawing, anidentical or corresponding element will be referred to as an identicalreference numeral.

Advantages and features of the disclosure and a method for achievingthem will be apparent with reference to embodiments of the disclosuredescribed below together with the attached drawings. However, thepresent disclosure is not limited to the disclosed embodiments, but maybe implemented in various manners, and the embodiments are provided tocomplete the disclosure of the present disclosure and to allow those ofordinary skill in the art to understand the scope of the presentdisclosure, and the scope to be claimed of the present disclosure isdefined by the category of the claims. Throughout the specification, anidentical reference numeral will indicate an identical element.

It will be understood that each block of the flowchart and/or blockdiagram illustrations, and combinations of blocks in the flowchartand/or block diagram illustrations, may be implemented by computerprogram instructions. These computer program instructions may also bestored in a general-purpose computer, a special-purpose computer, or aprocessor of other programmable data processing devices, such that theinstructions implemented by the computer or the processor of theprogrammable data processing device produce a means for performingfunctions specified in the flowchart and/or block diagram block orblocks. These computer program instructions may also be stored in acomputer usable or computer-readable memory that may direct a computeror other programmable data processing apparatus to function in aparticular manner, such that the instructions stored in the computerusable or computer-readable memory produce an article of manufactureincluding instructions that implement the function specified in theflowchart and/or block diagram block or blocks. The computer programinstructions may also be loaded onto a computer or other programmabledata processing apparatus to cause a series of operational steps to beperformed on the computer or other programmable apparatus to produce acomputer implemented process, such that the instructions that executethe computer or other programmable apparatus may provide steps forimplementing the functions specified in the flowchart and/or blockdiagram block or blocks.

In addition, each block represents a module, segment, or portion ofcode, which includes one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat in other implementations, the function(s) noted in the blocks mayoccur out of the order indicated. For example, two blocks shown insuccession may, in fact, be executed substantially concurrently or theblocks may sometimes be executed in the reverse order, depending on thefunctionality involved.

The term ‘unit’ used herein refers to a software or hardware elementsuch as a field-programmable gate array (FPGA), an application specificintegrated circuit (ASIC), etc., and ‘˜unit’ plays specific roles.However, the meaning of ‘˜unit’ is not limited to software or hardware.‘˜unit’ may advantageously be configured to reside on the addressablestorage medium and configured to reproduce one or more processors. Thus,a unit may include, by way of example, components, such as softwarecomponents, object-oriented software components, class components andtask components, processes, functions, attributes, procedures,subroutines, segments of program code, drivers, firmware, microcode,circuitry, data, databases, data structures, tables, arrays, andvariables. The functionality provided for in the components and‘˜unit(s)’ may be combined into fewer components and ‘˜unit(s)’ orfurther separated into additional components and ‘˜unit(s)’. Inaddition, components and ‘˜unit(s)’ may be implemented to execute one ormore CPUs in a device or a secure multimedia card.

Although the description of embodiments herein focuses primarily onwireless communication systems based on particular wireless accesstechniques, the subject matter of the present disclosure may also beapplicable to other communication systems or services having similartechnical backgrounds without departing from the scope of the presentdisclosure, and this may be determined by one of ordinary skill in theart.

In the present disclosure, embodiments related to a non-coherent jointtransmission (NCJT) mode will be representatively described, and in theNCJT mode, multiple data streams may be transmitted from multiple basestations (BSs) to the same user. However, embodiments of the presentdisclosure may be expanded when multiple CSI reports need to be derivedand fed back even in any coordinated multipoint (CoMP) mode or non-CoMPmode.

FIGS. 1A and 1B show, respectively, network configurations operating incoherent joint transmission and non-coherent joint transmission schemes.

Referring to FIG. 1A, data for a user equipment (UE) 106 may betransmitted from multiple transmission points (TPs) (herein, two TPs,i.e., a TP A 102 and a TP B 104 are shown). The TP A 102 and the TP B104 may transmit radio signals for the UE 106 by using the same antennaports and/or the same radio resources, e.g., demodulation referencesignal (DMRS) ports 7 and 8. Each of the TPs 102 and 104 may be, forexample, a BS, a Node B (NB), or an enhanced Node B (eNB). CJT based onthe TPs 102 and 104 may be coordinated by a network entity 108. Thenetwork entity 108 may be implemented as, for example, a CoMP server.

Referring to FIG. 1B, data for a UE 116 may be independently transmittedfrom multiple TPs (herein, two TPs, i.e., a TP A 112 and a TP B 114 areshown). The TP A 112 and the TP B 114 may transmit radio signals for theUE 116 by using independent antenna ports and/or independent radioresources, e.g., the DMRS ports 7 and 8. Each of the TPs 112 and 114 maybe, for example, a BS, an NB, or an eNB. NCJT based on the TPs 112 and114 may be coordinated by a network entity 118. The network entity 118may be implemented as, for example, a CoMP server.

FIG. 2 shows signal and interference hypotheses (or network coordinationmethods) that may be used to derive CSI.

Referring to FIG. 2, G₁ and G₂ respectively denote time-frequencyresources corresponding to two TPs, i.e., a TP A (or referred to as aTRP A) and a TP B (or referred to as a TRP B). Depending on schedulingdecision, a modulation and coding scheme (MCS) applied to transmissionbased on each TP should be selected considering these differentinterference types corresponding to the hypotheses. Shown signal andinterference hypotheses 1 through 5 may be used to derive CSI that maybe used for scheduling decision. The UE may measure at least one of thehypotheses 1 through 5 and derive the CSI based on a measurement result.At least one CSI report including the derived CSI may be transmitted toa serving TP or all or at least two coordinating TPs.

In the hypothesis 1, the TP A may transmit a signal for UE 1 through G₁,and the TP B may transmit a signal (that may be the same) for UE 1 byusing G₂. In the hypothesis 2, the TP A may transmit a signal for UE 1in G₁, and G₂ is blanked. The blanked G₂ may be used for interferencemeasurement. In the hypothesis 3, the TP B may transmit a signal for UE1 through G₂, and G₁ is blanked. The blanked G₁ may be used forinterference measurement. In the hypothesis 4, the TP A may transmit asignal for UE 1 in G₁, and may work as interference with a signal for UE2 transmitted by the TP B in G₂. In the hypothesis 5, the TP A maytransmit a signal for UE 1 in G1, and may work as interference with asignal for UE 2 transmitted by the TP B in G₂.

For example, the BS may be configured to use NCJT for a first UE, UE 1,in one subframe, but the eNB may be configured to use dynamic pointselection (DPS) for UE 1 in another subframe. In still another subframe,the BS may co-schedule a second UE, UE 2, as well as UE 1. To cope withthese various interference scenarios, CSI feedback should be flexiblydesigned for feCoMP (further enhancements to CoMP). For UE's feedback tofacilitate NCJT, a plurality of channel state information-referencesignal (CSI-RS) resources and a plurality of CSI-interferencemeasurement (CSI-IM) resources may be used. Examples of the CSI-RSresources and the CSI-IM resources are provided below.

-   -   A first CSI-RS resource used to estimate a channel of TP A;    -   A second CSI-RS resource used to estimate a channel of TP B;    -   A first CSI-IM resource used to estimate interference        corresponding to interference types 1, 2, and 3;    -   A second CSI-IM resource used to estimate interference        corresponding to interference type 4; and    -   A third CSI-IM resource used to estimate interference        corresponding to interference type 5.

Embodiments of the disclosure may relate to both CSI framework and CSIacquisition in CoMP for both 3GPP Long Term Evolution (LTE) and NewRadio (NR).

The precoding and resource allocation of the coordinating TRPs involvingCoMP may depend on CSI acquired from a UE and feedback by the UE. ForNCJT from a plurality of TRPs, the UE may be configured to report oneCSI or multiple CSI based on a plurality of signal and interferencehypotheses (or network coordination methods), by upper-layer signaling,for example, radio resource control (RRC).

There may be options for CSI reporting of the UE as below.

1. Full set reporting: the UE reports CSIs respectively corresponding toall hypotheses;

2. Subset reporting: a network (e.g., an upper layer of a BS)dynamically triggers which CSI report or which subset of CSI report tobe feedback.

In both options, multiple CSI reports are needed and a feedback overheadis therefore large. Through at least one of embodiments described below,signaling overhead is reduced, especially for the first option where theUE needs to feedback many CSI reports (e.g., 5 CSI reports correspondingto the hypotheses of FIG. 2), resulting in a possibly significantsignaling overhead.

Embodiments of the disclosure may include sending, from a BS to a UE, aninformation element (IE) containing a list of measurement objects thatdefine configurations of CSI-RS based radio resource management (RRM)measurements.

When a CSI report is triggered by the network and the UE needs to reporta plurality of CSI reports (first option), these reports may be fed backseparately in an independent manner, which may create a significantfeedback signaling overhead. For the hypothesis 1 where two TRPstransmit the same signal to UE 1, the interference experienced by UE 1when UE 1 decodes a data stream from the TRP A may be expressed as:I _(H1) =I _(TRP21) +I _(TRP_12) +N  [Equation 1]

I_(Hi) is the interference received by UE 1 in hypothesis i, I_(TRP21)is the interference from TRP B to UE 1 when TRP B transmits to UE 1,I_(TRP_12) is the interference from all other TRPs except for the TRP Aand the TRP B, and N is the thermal noise.

For the hypothesis 2 where only the TRP A transmits to UE 1 and the TRPB stays silent, the interference experienced by UE 1 is:I _(H2) =I _(TRP_12) +N  [Equation 2]

For the hypothesis 3 where only the TRP A transmits to UE 1 and the TRPB transmits to UE 2, the interference experienced by UE 1 is:I _(H4) =I _(TRP22) +I _(TRP_12) +N  [Equation 3]

I_(TRP22) is the interference from TRP B to UE 1 when TRP B transmits toUE 2.

From the above equations (1)-(3), it may be found that the interferencelevels of these hypotheses are not independent from each other butcorrelated in the sense that they have a common term I_(TRP_12), whichmeans the corresponding CSI reports are also correlated.

This correlation between CSI reports can be exploited to reduce afeedback overhead.

One way to reduce the feedback overhead may be to feedback at least twocorrelated CSI reports together as a comprehensive CSI report. Forexample, one full CSI report and an ‘offset’ CSI report may be fed backto the serving TP from the UE. The full CSI report is referred to as aprimary CSI report and the ‘offset’ report is referred to as a secondaryCSI report. Each CSI report may include at least one of a channelquality indicator (CQI), a precoding matrix indicator (PMI), or a rankindicator according to a configuration based on a network.

The CQI may denote an MCS for a required block error rate (BLER) of achannel. The PMI may denote a precoding matrix indicating a scheme inwhich individual data streams (e.g., layers) are mapped to antennaports. The RI may denote the number of layers transmitted and the numberof different signal streams.

Next, an embodiment using CQI as an example will be described. For thehypothesis 2, the interference may exist from other TRPs only, and forthe hypothesis 4, the interference may exist from other TRPs and the TRPB. When two CSI reports are needed, UE 1 may transmit a full CQI valuefor the hypothesis 2 (a primary CSI report) and an ‘offset’ CQI valuefor the hypothesis 4 (a secondary CSI report), based on the identifiedcorrelation between the two hypotheses (the hypotheses 2 and 4).

In other words, UE 1 may transmit a CSI report including CQI₂, which isthe CQI value for the hypothesis 2, and Δ_(CQI), which is the CQI‘offset’ between the hypothesis 2 and the hypothesis 4, caused by theadditional interference from the TRP B to UE 1 when the TRP B transmitsto UE 2. The CSI report may be transmitted to the serving BS, the TRP A,or to both the TRP A and the TRP B.

The TRPs may receive the CSI report, and acquire CQI₄ by usingCQI₂+Δ_(CQI) included in the received CSI report, in which CQI₄ is a CQIfor the hypothesis 4. To acquire CQI₄, each TRP may use a correlationbetween CSI reports corresponding to the identified correlation betweenthe two hypotheses (the hypotheses 2 and 4) shared with UE 1. Since therange of Δ_(CQI) may be much smaller than the range pf values expectedfor CQI₂, fewer bits are needed to indicate Δ_(CQI). Therefore, theamount of feedback bits for CSI reporting may be reduced.

The CQI calculation may be treated as a quantization step to convertcontinuous CQI values into a limited number of bins, thus limiting afeedback overhead. A more efficient way to exploit the correlationbetween CSI reports is Slepian-Wolf coding (SWC). Slepian-Wolf codinghas been selected since it is well known and relatively simple toimplement. A skilled person will appreciate that other coding schemes,e.g., Wyner-Ziv coding, which exploit the correlation between theprimary and secondary reports may be used instead.

SWC can be explained in a simple example as follows. Assume X and Y areequiprobable binary triplets with X, Yϵ{0, 13}³ that differ at most inone position. The entropies of X and Y are equal to 3 bits. When X and Yare encoded separately, 6 bits are required.

If Y is known, only four choices of X with equal probability areavailable. For example, when Y=000, Xϵ{000, 100, 010, 001}. Hence, only2 extra bits are needed to indicate X The conditional entropy H(X|Y) isequal to 2 bits. For joint encoding of X and Y, three bits are needed toconvey Y and two additional bits are needed to index the four possiblechoices of X associated with Y, such that instead of H(Y)+H(X)=6 bits, atotal of H(X,Y)=H(Y)+H(X|Y)=5 bits are sufficient.

The same principle can be applied to CSI feedback, e.g., CQI feedback.When CQI calculation is treated as a quantization procedure, the minimalnumber of bits to carry a CQI feedback may be expressed as the entropyof CQI, H(CQI), as below.R _(in) =H(CQI ₁)+H(CQI ₂)+H(CQI ₄)  [Equation 4]

R_(in) is the total number of bits needed and H(CQI_(i)) is the entropyof CQI value for interference hypothesis i.

When SW coding is used, the number of bits needed for the CQI feedbackis as follows:R _(sw) =H(CQI ₄ |CQI ₁ ,CQI ₂)+H(CQI ₁ |CQI ₂)+H(CQI ₂)  [Equation 5]

R_(sw) is the total number of bits needed when SWC is used, andH(CQI_(i)|CQI_(j)) is the conditional entropy of CQI i conditioned onCQI j. The entropy has the following characteristics:H(CQI ₄ |CQI ₁ ,CQI ₂)+H(CQI ₁ |CQI ₂)+H(CQI ₂)≤H(CQI ₁)+H(CQI ₂)+H(CQI₄)  [Equation 6]

Therefore, R_(sw)≤R_(in), which means a smaller number of bits isrequired for a CQI feedback when SWC is used.

FIGS. 3A and 3B are flowcharts of a CSI feedback procedure of a UE,according to an embodiment of the present disclosure.

Referring to FIG. 3A, in operation S300, a UE may receive configurationinformation related to at least one CSI report from a BS (or at leasttwo BSs associated with CoMP transmission of the UE). For example, theconfiguration information may be associated with a particulartransmission mode, e.g., an NCJT mode or a CoMP mode. The UE may alsoreceive configuration information indicating enabling of a particulartransmission mode, e.g., the NCJT mode. Each piece of configurationinformation may be delivered by, for example, upper-layer signaling ordownlink control information.

In operation S310, a determination may be made as to whether multipleCSI reports are configured by the configuration information. When asingle CSI report is configured, the UE may generate the single CSIreport based on the configuration information in operation S330 and goto operation S340. When a plurality of CSI reports are configured, theUE may generate the plurality of CSI reports based on the configurationinformation in operation S330 and go to operation S340.

The single CSI report or the plurality of CSI reports generated inoperation S340 may be transmitted from the UE to the BS(s) based on theconfiguration information. The BS may receive the single CSI report orthe plurality of CSI reports and schedule transmission to the UE. In anembodiment, when the plurality of CSI reports are received, the BS maydetermine CSI for each measurement resource configured for the UE byusing a correlation between the CSI reports.

FIG. 3B shows detailed operations of operation S320 of FIG. 3A accordingto an embodiment of the disclosure.

Referring to FIG. 3B, in operation S322, a plurality of CSI reports fora plurality of measurement resources configured for the UE may bedivided into two groups, e.g., a first group to which compression is notapplied (at least one primary CSI report) and a second group to whichcompression is applied (at least one secondary CSI report).

In operation S324, the UE may compress a CSI report of the second group(the secondary CSI report). The compression may be performed, using acorrelation between the primary CSI report and the secondary CSI reportand correlated coding schemes, e.g., SWC. The UE may generate acomprehensive CSI report including the primary CSI report and thecompressed secondary CSI report, in which the comprehensive CSI reportmay be transmitted from the UE to the BS in operation S340.

The comprehensive CSI report provided from the UE to the BS may includeat least one primary CSI report and at least one secondary CSI reportbased on a configuration from the BS. In an embodiment, at least oneprimary CSI report may be provided in a non-compressed format. In anembodiment, at least one secondary CSI report may be compressed.

One or more secondary CSI reports may be derived, based on a correlationwith one or more primary CSI reports. In an embodiment, a single primaryCSI report may be used as the basis for a plurality of secondary CSIreports. In an embodiment, the plurality of primary CSI reports are usedas a basis for the single secondary CSI report, or the plurality ofprimary CSI reports may be used as a basis for the plurality ofsecondary CSI reports.

When receiving the comprehensive CSI report from the UE, the BS maydecompress/derive at least one secondary CSI report included in thecomprehensive CSI report to extract information included therein, e.g.,at least one of a CQI, a PMI, or an RI.

FIGS. 4A and 4B are flowcharts of a CSI feedback reception procedure ofa BS, according to an embodiment of the present disclosure.

Referring to FIG. 4A, in operation S400, the BS may transmitconfiguration information related to at least one CSI report configuredfor the UE to the UE. For example, the configuration information may beassociated with a particular transmission mode, e.g., an NCJT mode or aCoMP mode. The BS may also transmit configuration information indicatingthat a particular transmission mode, e.g., the NCJT mode is possible tothe UE. Each configuration information may be transmitted to the UE byat least two BSs related to CoMP transmission of the UE. Each piece ofconfiguration information may be delivered by, for example, upper-layersignaling or downlink control information.

In operation S410, the BS may determine whether a plurality of CSIreports for the UE is configured by the configuration information. Whenthe single CSI report is configured, the BS may receive and derive thesingle CSI report from the UE based on the configuration information inoperation S430. When the plurality of CSI reports are configured, the BSmay receive and derive the plurality of CSI reports transmitted from theUE based on the configuration information in operation S420. In anembodiment, the BS may determine CSI for each measurement resourceconfigured for the UE by using a correlation between the plurality ofCSI reports.

FIG. 4B shows detailed operations of operation S420 of FIG. 4A accordingto an embodiment of the disclosure.

Referring to FIG. 4B, in operation S422, the BS may receive acomprehensive CSI report including at least one primary CSI report andat least one secondary CSI report from the UE. In operation S424, the BSmay decompress/derive the at least one secondary report(s) to yield allrequired CSI information.

FIG. 5 is a block diagram of a UE according to an embodiment of thepresent disclosure.

Referring to FIG. 5, the UE may include a transceiver 510, at least oneprocessor 520, and a memory 530. The transceiver 510 may exchange aradio signal with one or more BSs (or TPs or TRPs). The processor 520may be configured to operate according to at least one combination or atleast two combinations of the above-described embodiments of thedisclosure. For example, the processor 520 may acquire configurationinformation received from the BS, generate a single CSI report or aplurality of CSI reports for an enabled operation mode (e.g., the NCJTmode) based on the configuration information, and transmit the generatedreport(s) to the BS, according to the embodiment of FIGS. 3A and 3B. Thememory 530 may store a parameter, data, and a program code needed for anoperation of the processor 520.

FIG. 6 is a block diagram of a base station (BS) according to anembodiment of the present disclosure.

Referring to FIG. 6, the BS may include a transceiver 610, at least oneprocessor 620, and a memory 630. The transceiver 610 may exchange aradio signal with the UE. The processor 620 may be configured to operateaccording to at least one combination or at least two combinations ofthe above-described embodiments of the disclosure. For example, theprocessor 620 may transmit configuration information for the UE to theUE and receive a single CSI report or a plurality of CSI reports for anenabled operation mode (e.g., the NCJT mode) from the UE based on theconfiguration information, according to the embodiment of FIGS. 4A and4B. The memory 630 may store a parameter, data, and a program codeneeded for an operation of the processor 620.

Embodiments of the disclosure may reduce the amount of channel statefeedback information that needs to be delivered from the UE to the BS(s)for an operation in the NCJT mode that may need a significant amount offeedback information.

Various embodiments of the present disclosure may also be implemented asa computer readable code in a computer readable recording medium inparticular aspects. The computer readable recording medium may be anytype of data storage device that may store data readable by a computersystem. Examples of recording mediums readable by the computer mayinclude a read-only memory (ROM), a random access memory (RAM), acompact disc-ROM (CD-ROM), magnetic tapes, floppy disks, optical datastorage devices, carrier waves (such as data transmission through theInternet). The computer readable recording medium may be distributedthrough computer systems connected over a network, and thus the computerreadable code is stored and executed in a decentralized manner. Further,functional programs, codes and code segments for achieving the presentdisclosure may be easily interpreted by programmers skilled in the artwhich the present disclosure pertains to.

The apparatus and method according to various embodiments of the presentdisclosure may be implemented by hardware, software, or a combination ofhardware and software. Such software may be stored, whether or noterasable or re-recordable, in a volatile or non-volatile storage such asa read-only memory (ROM), a memory such as a random access memory (RAM),a memory chip, a device, or an integrated circuit; and an optically ormagnetically recordable and machine (e.g., computer)—readable storagemedium such as a compact disc (CD), a digital versatile disk (DVD), amagnetic disk, or a magnetic tape. It can be seen that the methodaccording to the present disclosure may be implemented by a computer ora portable terminal which includes a controller and a memory, and thememory is an example of a machine-readable storage medium which issuitable for storing a program or programs including instructions forimplementing the embodiment of the present disclosure.

Accordingly, the present disclosure includes a program that includes acode for implementing the apparatus and method set forth in the appendedclaims of the specification and a machine (computer, etc.) readablestorage medium for storing the program. The program may beelectronically transferred through an arbitrary medium such as acommunication signal delivered through a wired or wireless connection,and the present disclosure properly includes equivalents thereof.

The apparatus according to an embodiment of the present disclosure mayreceive and store the program from a program providing device connectedin a wired or wireless manner. The program providing device may includea memory for storing a program including instructions for instructingthe apparatus to execute a preset method, information necessary for themethod, a communication unit for performing wired or wirelesscommunication with the apparatus, and a controller for transmitting acorresponding program to the apparatus at the request of the apparatusor automatically.

Meanwhile, the embodiments disclosed in the present specification anddrawings have been provided to easily describe the present disclosureand to help with the understanding of the present disclosure, and arenot intended to limit the scope of the present disclosure. While theforegoing embodiments of the present disclosure have been shown anddescribed as examples, it will be apparent to those of ordinary skill inthe art that modifications and variations can be made without departingfrom the spirit and scope of the embodiments as defined by the appendedclaims. Therefore, the true technical scope of the present disclosureshould be defined by the appended claims.

The invention claimed is:
 1. A method of transmitting channel stateinformation (CSI) by a user equipment (UE) in a communication system,the method comprising: receiving, from a base station (BS),configuration information via radio resource control (RRC) signaling,the configuration information comprising information indicating whetherCSI feedback based on a non-coherent joint transmission (NCJT) mode isconfigured to the UE; generating a first CSI and a second CSI, inresponse to identifying that the CSI feedback based on the NCJT mode isconfigured by the configuration information; and transmitting the firstCSI and the second CSI to the BS, wherein, in case that the CSI feedbackbased on the NCJT mode is configured, the configuration informationincludes information configuring two CSI reference signal (CSI-RS),resources and information configuring at least one CSI interferencemeasurement (CSI-IM), resource, and wherein the two CSI-RS resourcesinclude a first CSI-RS resource corresponding to the first CSI and asecond CSI-RS resource corresponding to the second CSI.
 2. The method ofclaim 1, wherein the first CSI comprises non-compressed CSI, and thesecond CSI comprises compressed CSI.
 3. The method of claim 1, whereinthe second CSI is generated using a correlation between the first CSIand the second CSI.
 4. The method of claim 1, wherein the second CSIcomprises CSI compressed by Slepian-Wolf coding.
 5. The method of claim1, wherein each of the first CSI and the second CSI includes at leastone of a channel quality information (CQI), a precoding matrix indicator(PMI), or a rank indicator (RI).
 6. A user equipment (UE) that transmitschannel state information (CSI) in a communication system, the UEcomprising: a transceiver configured to receive, from a base station(BS), configuration information via radio resource control (RRC)signaling, the configuration information comprising informationindicating whether CSI feedback based on a non-coherent jointtransmission (NCJT) mode is configured to the UE; and a processorconfigured to generate a first CSI and a second CSI, in response toidentifying that the CSI feedback based on the NCJT mode is configuredby the configuration information, and transmit, to the BS, the first CSIand the second CSI, wherein, in case that the CSI feedback based on theNCJT mode is configured, the configuration information includesinformation configuring two CSI reference signal (CSI-RS), resources andinformation configuring at least one CSI interference measurement(CSI-IM), resource, and wherein the two CSI-RS resources include a firstCSI-RS resource corresponding to the first CSI and a second CSI-RSresource corresponding to the second CSI.
 7. The UE of claim 6, whereinthe first CSI comprises non-compressed CSI, and the second CSI comprisescompressed CSI, and wherein the second CSI is compressed using acorrelation between the first CSI and the second CSI.
 8. The UE of claim6, wherein the second CSI comprises CSI compressed by Slepian-Wolfcoding.
 9. The UE of claim 6, wherein each of the first CSI and thesecond CSI includes at least one of a channel quality information (CQI),a precoding matrix indicator (PMI), or a rank indicator (RI).
 10. Amethod of receiving channel state information (CSI) by a base station(BS) in a communication system, the method comprising: transmitting, toa user equipment (UE), configuration information via radio resourcecontrol (RRC) signaling, the configuration information comprisinginformation indicating whether a CSI feedback based on a non-coherentjoint transmission, NCJT, mode is configured to the UE; receiving afirst CSI and a second CSI from the UE in case that the CSI feedbackbased on the NCJT mode is configured to the UE based on theconfiguration information; and processing the first CSI and the secondCSI, wherein, in case that the CSI feedback based on the NCJT mode isconfigured, the configuration information includes informationconfiguring two CSI reference signal, CSI-RS, resources and informationconfiguring at least one CSI interference measurement, CSI-IM, resource,and wherein the two CSI-RS resources include a first CSI-RS resourcecorresponding to the first CSI and a second CSI-RS resourcecorresponding to the second CSI.
 11. The method of claim 10, wherein thefirst CSI comprises non-compressed CSI, and the second CSI comprisescompressed CSI.
 12. The method of claim 10, wherein the second CSI isgenerated using a correlation between the first CSI and the second CSI.13. The method of claim 10, wherein the second CSI comprises CSIcompressed by Slepian-Wolf coding.
 14. The method of claim 10, whereineach of the first CSI and the second CSI includes at least one of achannel quality information (CQI), a precoding matrix indicator (PMI),or a rank indicator (RI).
 15. An apparatus of a base station (BS) thatreceives channel state information (CSI) in a communication system, theapparatus comprising: a transceiver configured to transmit, to a userequipment (UE), configuration information via radio resource control(RRC) signaling, the configuration information comprising informationindicating whether a CSI feedback based on a non-coherent jointtransmission, NCJT, mode is configured to the UE; and a processorconfigured to process a first CSI and second CSI, wherein, in case thatthe CSI feedback based on the NCJT mode is configured, the configurationinformation includes information configuring two CSI reference signal,CSI-RS, resources and information configuring at least one CSIinterference measurement, CSI-IM, resource, and wherein the two CSI-RSresources include a first CSI-RS resource corresponding to the first CSIand a second CSI-RS resource corresponding to the second CSI.
 16. Theapparatus of claim 15, wherein the first CSI comprises non-compressedCSI, and the second CSI comprises compressed CSI, and wherein the secondCSI is compressed using a correlation between the first CSI and thesecond CSI.
 17. The apparatus of claim 15, wherein the second CSIcomprises CSI compressed by Slepian-Wolf coding.
 18. The apparatus ofclaim 15, wherein each of the first CSI and the second CSI includes atleast one of a channel quality information (CQI), a precoding matrixindicator(PMI), or a rank indicator (RI).